Accelerated whole-breast radiation therapy (RT), which shortens radiation treatment duration by half, is proved to be as effective as conventional therapy for early-stage breast cancer patients. Whether a concomitant boost is needed remains a subject of debate among radiation oncologists due to the overall treatment's potential toxicity.
The latest findings from an ongoing, prospective study initiated in 2004 at Beth Israel Medical Center in New York City show encouraging results. Patients who received hypofractionated whole-breast irradiation delivered with a concomitant boost continue to have excellent local control and minimal side effects, according to an article published online January 4 in the International Journal of Radiation Oncology, Biology, Physics.
Study results were originally presented at the 2009 American Society for Radiation Oncology (ASTRO) annual meeting, where Dr. Manjeet Chadha, associate chair of the department of radiation oncology at Beth Israel, reported positive outcomes of the first 50 women enrolled. None of the women, all of whom were diagnosed with early-stage, node-negative breast cancer and who had undergone a lumpectomy, had experienced local recurrence or any acute severe toxicities at a median follow-up of two years.
Regarding the current findings, the number of participants had increased to 160. With a median follow-up of 3.5 years, and with some patients followed for nearly eight years, Chadha and colleagues reported a five-year local relapse-free survival rate of 99%. This exceeded the study's original estimate of a local relapse-free rate of 97%. Five-year overall survival was 90%, and disease-free survival was 97%.
The 160 patients ranged in age from 40 to 88 years. The majority of their invasive cancers were infiltrating duct cell histology, and the median tumor size was 2 cm (range, 0.2 cm to 3 cm). All but 12% were estrogen-receptor positive.
Patients enrolled in the hypofractionated radiotherapy program received a total dose of 45 Gy in 15 fractions over 19 days to the lumpectomy target volume. This included 40.5 Gy in 2.7-Gy fractions with a concomitant boost of 4.5 Gy in 0.3-Gy fractions. (Patients receiving conventional whole-breast irradiation received a dose of 46.8 Gy in 26 fractions and a sequential boost of 14 Gy in seven fractions.)
The first 50 patients and the additional 110 patients experienced a low incidence of skin toxicities: 70% of the patients experienced grade 1 toxicity, and 5% experienced grade 2. No patients developed a higher toxicity level, and only 39% experienced late grade 1 or 2 skin toxicities.
In 2011, the researchers reported that the first 50 patients receiving the accelerated treatment experienced a lower incidence of grade 2+ skin toxicities and reported less pain than a control group of 74 patients, who were treated during the same time period but received conventional whole-breast irradiation (Clinical Breast Cancer, February 2012, Vol. 12:1, pp. 57-62; online November 7, 2011). Rates of breast edema and fatigue were comparable.
"Based on data from other clinical trials, the observed skin toxicity of the patients enrolled in our prospective study appears to compare very favorably," Chadha told AuntMinnie.com. "Ongoing randomized clinical trials will evaluate this aspect in a prospective manner." She and her colleagues plan to publish detailed data on the cosmetic outcomes of these patients.
Chadha said that women who come to the Beth Israel radiation oncology department who clinically qualify for hypofractionated treatment are offered it.
"For early-stage invasive breast cancer, there is a mature body of data supporting an accelerated whole-breast radiation therapy treatment schedule," she said. "We routinely offer this option to eligible patients with unifocal, small cancers and negative margins for whom no chemotherapy treatment is planned. Patients diagnosed with ductal carcinoma in situ are invited to enroll in the study."
Not all patients accept the treatment, however.
"There are patients who prefer to be treated conventionally because this treatment regime has the longest proven follow-up," she said. "We honor their preference; however, we are pleased to now be able to say that hypofractionated accelerated radiotherapy treatment with a concomitant boost is well-tolerated and has shown comparable outcomes."
